Methods and procedures for high speed UE access

ABSTRACT

A terminal random access procedure is improved by allowing a mobile terminal to correctly map signature indexes onto cyclic shifted Zadoff-Chu (ZC) sequences when the deployed cells support a high-speed mobility by informing a mobile terminal whether a cell supports high-speed mobility.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/958,118, filed on Dec. 17, 2007, now U.S. Pat. No. 8,787,957, whichclaims the benefit of U.S. Provisional Application Ser. No. 60/889,520,filed on Feb. 12, 2007, the contents of which are hereby incorporated byreference herein in their entirety.

FIELD OF THE INVENTION

The present invention is directed to a mobile terminal random accessprocedure for obtaining uplink time synchronization and access to anetwork and specifically to an apparatus and method that allows a mobileterminal to correctly map signature indexes onto cyclic shiftedZadoff-Chu (ZC) sequences when the deployed cells support a high-speedmobility by informing a mobile terminal whether a cell supportshigh-speed mobility.

DESCRIPTION OF THE RELATED ART

A universal mobile telecommunication system (UMTS) is a European-type,third generation IMT-2000 mobile communication system that has evolvedfrom a European standard known as Global System for Mobilecommunications (GSM). UMTS is intended to provide an improved mobilecommunication service based upon a GSM core network and wideband codedivision multiple access (W-CDMA) wireless connection technology. InDecember 1998, a Third Generation Partnership Project (3GPP) was formedby the ETSI of Europe, the ARIB/TTC of Japan, the T1 of the UnitedStates, and the TTA of Korea. The 3GPP creates detailed specificationsof UMTS technology.

In order to achieve rapid and efficient technical development of theUMTS, five technical specification groups (TSG) have been created withinthe 3GPP for standardizing the UMTS by considering the independentnature of the network elements and their operations. Each TSG develops,approves, and manages the standard specification within a relatedregion. The radio access network (RAN) group (TSG-RAN) develops thestandards for the functions, requirements, and interface of the UMTSterrestrial radio access network (UTRAN), which is a new radio accessnetwork for supporting W-CDMA access technology in the UMTS.

FIG. 1 provides an overview of a UMTS network. The UMTS network includesa mobile terminal or user equipment (UE) 1, a UTRAN 2 and a core network(CN) 3.

The UTRAN 2 includes several radio network controllers (RNCs) 4 andNodeBs 5 that are connected via the L_(b) interface. Each RNC 4 controlsseveral NodeBs 5. Each NodeB 5 controls one or several cells, where acell covers a given geographical area on a given frequency.

Each RNC 4 is connected via the lu interface to the CN 3 or towards themobile switching center (MSC) 6 entity of the CN and the general packetradio service (GPRS) support Node (SGSN) 7 entity. RNCs 4 can beconnected to other RNCs via the I_(ur) interface. The RNC 4 handles theassignment and management of radio resources and operates as an accesspoint with respect to the CN 3.

The NodeBs 5 receive information sent by the physical layer of the UE 1via an uplink and transmit data to the UE 1 via a downlink. The Node-Bs5 operate as access points of the UTRAN 2 for the UE 1.

The SGSN 7 is connected to the equipment identity register (EIR) 8 viathe G_(f) interface, to the MSC 6 via the G_(S) interface, to thegateway GPRS support node (GGSN) 9 via the G_(N) interface, and to thehome subscriber server (HSS) via the G_(R) interface.

The EIR 8 hosts lists of UEs 1 that are allowed to be used on thenetwork. The EIR 8 also hosts lists of UEs 1 that are not allowed to beused on the network.

The MSC 6, which controls the connection for circuit switched (CS)services, is connected towards the media gateway (MGW) 11 via the N_(B)interface, towards the EIR 8 via the F interface, and towards the HSS 10via the D interface.

The MGW 11 is connected towards the HSS 10 via the C interface and alsoto the public switched telephone network (PSTN). The MGW 11 also allowsthe codecs to adapt between the PSTN and the connected RAN.

The GGSN 9 is connected to the HSS 10 via the G_(C) interface and to theInternet via the G_(I) interface. The GGSN 9 is responsible for routing,charging and separation of data flows into different radio accessbearers (RABs). The HSS 10 handles the subscription data of users.

The UTRAN 2 constructs and maintains an RAB for communication between aUE 1 and the CN 3. The CN 3 requests end-to-end quality of service (QoS)requirements from the RAB and the RAB supports the QoS requirements setby the CN 3. Accordingly, the UTRAN 2 can satisfy the end-to-end QoSrequirements by constructing and maintaining the RAB.

The services provided to a specific UE 1 are roughly divided into CSservices and packet switched (PS) services. For example, a general voiceconversation service is a CS service and a Web browsing service via anInternet connection is classified as a PS service.

The RNCs 4 are connected to the MSC 6 of the CN 3 and the MSC isconnected to the gateway MSC (GMSC) that manages the connection withother networks in order to support CS services. The RNCs 4 are connectedto the SGSN 7 and the gateway GGSN 9 of the CN 3 to support PS services.

The SGSN 7 supports packet communications with the RNCs. The GGSN 9manages the connection with other packet switched networks, such as theInternet.

FIG. 2 illustrates a structure of a radio interface protocol between aUE 1 and the UTRAN 2 according to the 3GPP radio access networkstandards. As illustrated In FIG. 2, the radio interface protocol hashorizontal layers comprising a physical layer, a data link layer, and anetwork layer, and has vertical planes comprising a user plane (U-plane)for transmitting user data and a control plane (C-plane) fortransmitting control information. The U-plane is a region that handlestraffic information with the user, such as voice or Internet protocol(IP) packets. The C-plane is a region that handles control informationfor an interface with a network as well as maintenance and management ofa call. The protocol layers can be divided into a first layer (L1), asecond layer (L2), and a third layer (L3) based on the three lowerlayers of an open system interconnection (OSI) standard model.

The first layer (L1), or physical layer, provides an informationtransfer service to an upper layer by using various radio transmissiontechniques. The physical layer is connected to an upper layer, or mediumaccess control (MAC) layer, via a transport channel. The MAC layer andthe physical layer exchange data via the transport channel.

The second layer (L2) includes a MAC layer, a radio link control (RLC)layer, a broadcast/multicast control (BMC) layer, and a packet dataconvergence protocol (PDCP) layer. The MAC layer handles mapping betweenlogical channels and transport channels and provides allocation of theMAC parameters for allocation and re-allocation of radio resources. TheMAC layer is connected to an upper layer, or the radio link control(RLC) layer, via a logical channel.

Various logical channels are provided according to the type ofinformation transmitted. A control channel is generally used to transmitinformation of the C-plane and a traffic channel is used to transmitinformation of the U-plane. A logical channel may be a common channel ora dedicated channel depending on whether the logical channel is shared.

FIG. 3 illustrates the different logical channels that exist. Logicalchannels include a dedicated traffic channel (DTCH), a dedicated controlchannel (DCCH), a common traffic channel (CTCH), a common controlchannel (CCCH), a broadcast control channel (BCCH), and a paging controlchannel (PCCH), or a Shared Control Channel (SCCH), as well as otherchannels. The BCCH provides information including information utilizedby a UE 1 to access a system. The PCCH is used by the UTRAN 2 to accessa UE 1.

Additional traffic and control channels are introduced in the MultimediaBroadcast Multicast Service (MBMS) standard for the purposes of MBMS.The MBMS point-to-multipoint control channel (MCCH) is used fortransmission of MBMS control information. The MBMS point-to-multipointtraffic channel (MTCH) is used for transmitting MBMS service data. TheMBMS scheduling channel (MSCH) is used to transmit schedulinginformation.

The MAC layer is connected to the physical layer by transport channels.The MAC layer can be divided into a MAC-b sub-layer, a MAC-d sub-layer,a MAC-c/sh sub-layer, a MAC-hs sub-layer and a MAC-m sublayer accordingto the type of transport channel being managed.

The MAC-b sub-layer manages a broadcast channel (BCH), which is atransport channel handling the broadcasting of system information. TheMAC-c/sh sub-layer manages a common transport channel, such as a forwardaccess channel (FACH) or a downlink shared channel (DSCH), which isshared by a plurality of UEs 1, or in the uplink the radio accesschannel (RACH). The MAC-m sublayer may handle MBMS data.

FIG. 4 illustrates the possible mapping between the logical channels andthe transport channels from a UE 1 perspective. FIG. 5 illustrates thepossible mapping between the logical channels and the transport channelsfrom a UTRAN 2 perspective.

The MAC-d sub-layer manages a dedicated channel (DCH), which is adedicated transport channel for a specific UE 1. The MAC-d sublayer islocated in a serving RNC 4 (SRNC) that manages a corresponding UE 1. OneMAC-d sublayer also exists in each UE 1.

The RLC layer supports reliable data transmissions and performssegmentation and concatenation on a plurality of RLC service data units(SDUs) delivered from an upper layer depending of the RLC mode ofoperation. The RLC layer adjusts the size of each RLC SDU received fromthe upper layer in an appropriate manner based upon processing capacityand then creates data units by adding header information. The dataunits, or protocol data units (PDUs), are transferred to the MAC layervia a logical channel. The RLC layer includes a RLC buffer for storingthe RLC SDUs and/or the RLC PDUs.

The BMC layer schedules a cell broadcast (CB) message transferred fromthe CN 3. The BMC layer broadcasts the CB message to UEs 1 positioned ina specific cell or cells.

The PDCP layer is located above the RLC layer. The PDCP layer is used totransmit network protocol data, such as the IPv4 or IPv6, efficiently ona radio interface with a relatively small bandwidth. The PDCP layerreduces unnecessary control information used in a wired network, afunction called header compression, for this purpose.

The radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is only defined in the C-plane. The RRC layercontrols the transport channels and the physical channels in relation tosetup, reconfiguration, and the release or cancellation of the radiobearers (RBs).

A RB signifies a service provided by the second layer (L2) for datatransmission between a UE 1 and the UTRAN 2. The set up of the RBgenerally refers to the process of stipulating the characteristics of aprotocol layer and a channel required for providing a specific dataservice and setting the respective detailed parameters and operationmethods. The RRC also handles user mobility within the RAN andadditional services, such as location services.

Not all different possibilities for the mapping between the RBs and thetransport channels for a given UE 1 are available all the time. The UE1/UTRAN 2 deduce the possible mapping depending on the UE state and theprocedure presently executed by the UE/UTRAN.

The different transport channels are mapped onto different physicalchannels. The configuration of the physical channels is given by RRCsignaling exchanged between the RNC 4 and the UE 1.

Initial access is a procedure whereby a UE 1 sends a first message tothe UTRAN 2 using a common uplink channel, specifically the RandomAccess Channel (RACH). For both GSM and UMTS systems, the initial accessprocedure involves the UE 1 transmitting a connection request messagethat includes a reason for the request and receiving a response from theUTRAN 2 indicating the allocation of radio resources for the requestedreason.

There are several reasons, or establishment causes, for sending aconnection request message. Table I indicates the establishment causesspecified in UMTS, specifically in 3GPP TS 25.331.

The “originating call” establishment cause indicates that the UE 1 wantsto setup a connection, for example, a speech connection. The“terminating call” establishment cause indicates that that UE 1 answersto paging. The “registration” establishment cause indicates that thatthe user wants to register only to the network.

A physical random access procedure is used to send information over theair. The physical random access transmission is under control of ahigher layer protocol, which performs important functions related topriority and load control. This procedure differs between GSM and UMTSradio systems.

The description of GSM random access procedure can be found in “The GSMSystem for Mobile Communications” published by M. Mouly and M. B.Pautet, 1992. As the present invention is related to UMTS enhancementand evolution, the W-CDMA random access procedure is detailed herein.Although the present invention is explained in the context of UMTSevolution, the present invention is not so limited.

The transport channel RACH and two physical channels, Physical RandomAccess Channel (PRACH) and Acquisition Indication Channel (AICH), areutilized in this procedure. The transport channels are channels suppliedby the physical layer to the protocol layer of the MAC layer. There areseveral types of transport channels to transmit data with differentproperties and transmission formats over the physical layer.

Physical channels are identified by code and frequency in FrequencyDivision Duplex (FDD) mode and are generally based on a layerconfiguration of radio frames and timeslots. The form of radio framesand timeslots depends on the symbol rate of the physical channel.

A radio frame is the minimum unit in the decoding process, consisting of15 time slots. A time slot is the minimum unit in the Layer 1 bitsequence. Therefore, the number of bits that can be accommodated in onetime slot depends on the physical channel.

TABLE I Establishment Causes Originating Conversational Call OriginatingStreaming Call Originating Interactive Call Originating Background CallOriginating Subscribed traffic Call Terminating Conversational CallTerminating Streaming Call Terminating Interactive Call TerminatingBackground Call Emergency Call Inter-RAT cell re-selection Inter-RATcell change order Registration Detach Originating High PrioritySignaling Originating Low Priority Signaling Call re-establishmentTerminating High Priority Signaling Terminating Low Priority Signaling

The transport channel RACH is an uplink common channel used fortransmitting control information and user data. The transport channelRACH is utilized in random access and used for low-rate datatransmissions from a higher layer. The RACH is mapped to an uplinkphysical channel, specifically the PRACH. The AICH is a downlink commonchannel, which exists as a pair with PRACH used for random accesscontrol.

The transmission of PRACH is based on a slotted ALOHA approach with fastacquisition indication. The UE randomly selects an access resource andtransmits a RACH preamble part of a random access procedure to thenetwork.

A preamble is a short signal that is sent before the transmission of theRACH connection request message. The UE 1 repeatedly transmits thepreamble by increasing the transmission power each time the preamble issent until it receives the Acquisition Indicator (AI) on AICH, whichindicates the detection of the preamble by the UTRAN 2. The UE 1 stopsthe transmission of the preamble once it receives the AI and sends themessage part at the power level equal to the preamble transmission powerat that point, adding an offset signaled by the UTRAN 2. FIG. 6illustrates a power ramping procedure.

This random access procedure avoids a power ramping procedure for theentire message. A power ramping procedure would create more interferencedue to unsuccessfully sent messages and would be less efficient due to alarger delay since it would take much more time to decode the messagebefore an acknowledgement could be transmitted to indicate successfulreceipt of the message.

The main characteristics of the RACH is that it is a contention basedchannel subject to collisions due to simultaneous access of severalusers, which may preclude decoding of the initial access message by thenetwork. The UE 1 can start the random access transmission of bothpreambles and message only at the beginning of an access slot. Thisaccess method is, therefore, a type of slotted ALOHA approach with fastacquisition indication

The time axis of both the RACH and the AICH is divided into timeintervals or access slots. There are 15 access slots per two frames,with each frame having a length of 10 ms or 38400 chips, and the accessslots are spaced 1.33 ms or 5120 chips apart. FIG. 7 illustrates thenumber and spacing of access slots.

The UTRAN 2 signals information regarding which access slots areavailable for random access transmission and the timing offsets to usebetween RACH and AICH, between two successive preambles and between thelast preamble and the message. For example, if the AICH transmissiontiming is 0 and 1, it is sent three and four access slots after the lastpreamble access slot transmitted, respectively. FIG. 8 illustrates thetiming of the preamble, AI and message part

The timing at which the UE 1 can send the preamble is divided by randomaccess sub channels. A random access sub channel is a subset includingthe combination of all uplink access slots. There are 12 random accesssub channels. A random access sub channel consists of the access slotsindicated in Table II.

TABLE II SFN modulo 8 of corre- sponding P-CCPCH Sub-channel numberframe 0 1 2 3 4 5 6 7 8 9 10 11 0 0 1 2 3 4 5 6 7 1 12 13 14 8 9 10 11 20 1 2 3 4 5 6 7 3 9 10 11 12 13 14 8 4 6 7 0 1 2 3 4 5 5 8 9 10 11 12 1314 6 3 4 5 6 7 0 1 2 7 8 9 10 11 12 13 14

The preamble is a short signal that is sent before the transmission ofthe RACH message. A preamble consists of 4096 chips, which is a sequenceof 256 repetitions of Hadamard codes of length 16 and scrambling codesassigned from the upper layer.

The Hadamard codes are referred to as the signature of the preamble.There are 16 different signatures and a signature is randomly selectedfrom available signature sets on the basis of Access Service Classes(ASC) and repeated 256 times for each transmission of the preamble part.Table III lists the preamble signatures.

The message part is spread by Orthogonal Variable Spreading Factor(OVSF) codes that are uniquely defined by the preamble signature and thespreading codes for use as the preamble signature. The 10 ms longmessage part radio frame is divided into 15 slots, each slot consistingof 2560 chips.

TABLE III Preamble Value of n signature 0 1 2 3 4 5 6 7 8 9 10 11 12 1314 15 P₀(n) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 P₁(n) 1 −1 1 −1 1 −1 1 −1 1−1 1 −1 1 −1 1 −1 P₂(n) 1 1 −1 −1 1 1 −1 −1 1 1 −1 −1 1 1 −1 −1 P₃(n) 1−1 −1 1 1 −1 −1 1 1 −1 −1 1 1 −1 −1 1 P₄(n) 1 1 1 1 −1 −1 −1 −1 1 1 1 1−1 −1 −1 −1 P₅(n) 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 P₆(n) 1 1 −1−1 −1 −1 1 1 1 1 −1 −1 −1 −1 1 1 P₇(n) 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −11 1 −1 P₈(n) 1 1 1 1 1 1 1 1 −1 −1 −1 −1 −1 −1 −1 −1 P₉(n) 1 −1 1 −1 1−1 1 −1 −1 1 −1 1 −1 1 −1 1 P₁₀(n) 1 1 −1 −1 1 1 −1 −1 −1 −1 1 1 −1 −1 11 P₁₁(n) 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 P₁₂(n) 1 1 1 1 −1 −1 −1−1 −1 −1 −1 −1 1 1 1 1 P₁₃(n) 1 −1 1 −1 −1 1 −1 1 −1 1 −1 1 1 −1 1 −1P₁₄(n) 1 1 −1 −1 −1 −1 1 1 −1 −1 1 1 1 1 −1 −1 P₁₅(n) 1 −1 −1 1 −1 1 1−1 −1 1 1 −1 1 −1 −1 1

Each slot includes a data part and a control part that transmits controlinformation, such as pilot bits and TFCI. The data part and the controlpart are transmitted in parallel. The 20 ms long message part consistsof two consecutive message part radio frames. The data part consists of10*2 k bits, where k=0, 1, 2, 3, which corresponds to a Spreading Factor(SF) of 256, 128, 64, 32. FIG. 9 illustrates the structure of the randomaccess message part.

The AICH consists of a repeated sequence of 15 consecutive access slots,each slot having a length of 40 bit intervals or 5120 chips. Each accessslot includes two parts, an Acquisition Indicator (AI) part consistingof 32 real-valued signals, such as a0 . . . a31, and a part having alength of 1024 chips during which transmission is switched off. FIG. 10illustrates the structure of the AICH.

When the UTRAN 2 detects transmission of a RACH preamble having acertain signature in an RACH access slot, the UTRAN repeats thissignature in the associated AICH access slot. Therefore, the Hadamardcode used as the signature for the RACH preamble is modulated onto theAI part of the AICH.

The acquisition indicator corresponding to a signature can have a valueof +1, −1 or 0 depending on whether a positive acknowledgement (ACK), anegative acknowledgement (NACK) or no acknowledgement is received inresponse to a specific signature. The positive polarity of the signatureindicates that the preamble has been acquired and the message can besent.

The negative polarity indicates that the preamble has been acquired andthe power ramping procedure shall be stopped, but the message shall notbe sent. This negative acknowledgement is used when a received preamblecannot be processed at the present time due to congestion in the UTRAN 2and the UE 1 must repeat the access attempt some time later.

All UEs 1 are members of one of ten randomly allocated mobilepopulations, defined as Access Classes (AC) 0 to 9. The populationnumber is stored in the Subscriber Identity Module (SIM)/UniversalSubscriber Identity Module (USIM). UEs 1 may also be members of one ormore out of 5 special categories of Access Classes 11 to 15, which areallocated to specific high priority users and the information alsostored in the SIM/USIM. Table IV lists the special AC and theirallocation.

TABLE IV AC Allocation 15 PLMN Staff 14 Emergency Services 13 PublicUtilities (e.g. water/gas suppliers) 12 Security Services 11

The UTRAN 2 performs the random access procedure at protocol layer L2 bydetermining whether to permit the UE 1 to use a radio access resourcebased primarily upon the AC to which the UE belongs.

It will be desirable to prevent UE 1 users from making access attempts,including emergency call attempts, or responding to pages in specifiedareas of a Public Land Mobile Network (PLMN) under certaincircumstances. Such situations may arise during states of emergency orwhere 1 or more co-located PLMNs has failed. Broadcast messages shouldbe available on a cell-by-cell basis to indicate the class(es) ofsubscribers barred from network access. The use of this facility allowsthe network operator to prevent overload of the access channel undercritical conditions

Access attempts are allowed if the UE 1 is a member of at least one ACthat corresponds to the permitted classes as signaled over the airinterface and the AC is applicable in the serving UTRAN 2. Accessattempts are otherwise not allowed. Any number of these AC may be barredat any one time. Access Classes are applicable as indicated in Table V.

TABLE V AC Applicability 0-9 Home and Visited PLMNs 11 and 15 Home PLMNonly 12, 13, 14 Home PLMN and visited PLMNs of home country only

An additional control bit for AC 10 is also signaled over the airinterface to the UE 1. This control bit indicates whether access to theUTRAN 2 is allowed for Emergency Calls for UEs 1 with access classes 0to 9 or without an International Mobile Subscriber Identity (IMSI).Emergency calls are not allowed if both AC 10 and the relevant AC, 11 to15 are barred for UEs 1 with access classes 11 to 15. Emergency callsare otherwise allowed.

The AC are mapped to ASC In the UMTS. There are eight different prioritylevels defined, specifically ASC 0 to ASC 7, with level 0 representingthe highest priority.

Access Classes shall only be applied at initial access, such as whensending an RRC Connection Request message. A mapping between AC and ASCshall be indicated by the information element “AC-to-ASC mapping” inSystem Information Block type 5. The correspondence between AC and ASCis indicated in Table VI.

TABLE VI AC 0-9 10 11 12 13 14 15 ASC 1^(st) IE 2^(nd) IE 3^(rd) IE4^(th) IE 5^(th) IE 6^(th) IE 7^(th) IE

In Table VI, “nth IE” designates an ASC number i in the range 0-7 to AC.The UE 1 behavior is unspecified if the ASC indicated by the “nth IE” isundefined.

The parameters implied by the respective ASC are utilized for randomaccess. A UE 1 that is a member of several ACs selects the ASC for thehighest AC number. The AC is not applied in connected mode.

An ASC consists of a subset of RACH preamble signatures and access slotsthat are allowed for the present access attempt and a persistence valuecorresponding to a probability, Pv≦1, to attempt a transmission. Anotherimportant mechanism to control random access transmission is a loadcontrol mechanism that reduces the load of incoming traffic when thecollision probability is high or when the radio resources are low. Aflow chart of the control access procedure is illustrated in FIG. 11.

Existing specifications provide many RACH transmission controlparameters that are stored and updated by the UE 1 based on systeminformation broadcast by the UTRAN 2. These parameters are received fromRRC (S10). The RACH transmission control parameters include PRACH, ASC,maximum number of preamble ramping cycles (M_(max)), range of backoffinterval for timer (T_(BO1)) specified as a number of 10 ms transmissiontime intervals (N_(BO1max)) and (N_(BO1min)) and applicable when NACK isreceived on AICH.

When it is determined that there is data to transmit (S20), the UE 1maps the assigned AC to an ASC (S30). A count value M is then set tozero (S40).

The count value M is then incremented by one (S50). The UE 1 determinesif the count value M, which represents the maximum number of RACHtransmission attempts, exceeds the maximum number of permitted RACHtransmission attempts M_(max) (S60).

The UE 1 treats the transmission as unsuccessful if M exceeds M_(max).The UE 1 then indicates the unsuccessful transmission to a higher layer(S70)

However, the UE 1 proceeds with the RACH access procedure if M is lessthan or equal to M_(max). The UE 1 updates the RACH transmission controlparameters (S80). A 10 ms timer T₂ is set (S90) and the UE 1 determineswhether to attempt transmission based on the persistence value P_(i)associated with the ASC selected by the UE.

Specifically, a random number between 0 and 1, R_(i), is generated(S100) and the random number is compared to the persistence value(S110). The UE 1 does not attempt transmission if R_(i) is less than orequal to the persistence value P_(i) and waits until the 10 ms timer T₂expires (S120) before repeating the RACH access procedure by updatingthe RACH transmission control parameters (S80). However, the UE 1attempts to transmit using assigned RACH resources (S130) if R_(i) isless than or equal to the persistence value P.

The UE 1 determines whether the response from the network is anAcknowledgement (ACK), a Non-Acknowledgment (NACK) or no response (S150)after the access attempt is transmitted. The UE 1 begins messagetransmission (S160) if an ACK is received, thereby indicating receipt ofthe UE transmission by the UTRAN 2. The UE 1 does not transmit themessage and repeats the RACH access procedure by incrementing the countvalue M (S50) if no response is received or a NACK is received, therebyindicating a failed receipt of the transmission by the network, forexample, due to a collision.

The UE 1 only waits until the 10 ms timer T₂ expires (S170) beforerepeating the RACH access procedure if no response was received.However, the UE 1 waits until the 10 ms timer T₂ expires (S180) and alsorandomly generates a back off value N_(BO1) associated with the PRACHassigned to the UE and between N_(BO1max) and N_(BO1min) and waits anadditional back off interval T_(BO1) that is equal to 10 ms multipliedby the back off value N_(BO1) (S190) before repeating the RACH accessprocedure if a NACK was received.

The physical layer (L1) random access procedure is initiated uponrequest from the MAC sub layer (L2). The physical layer receivesinformation from a higher layer, specifically the RRC, before thephysical random-access procedure is initiated and receives informationfrom a higher layer, specifically the MAC, at each initiation of thephysical random access procedure. The information is indicated in TableVII. The physical layer random-access procedure is illustrated in FIG.12.

As illustrated in FIG. 12, one access slot in the random accesssubchannel that can be used for the given ASC is randomly selected fromaccess slots that can be used in the next full access slot sets (S200).One access slot is randomly chosen from access slots that can be used inthe next full access slot sets if there are no access slots available.One signature is then randomly selected from the set of availablesignatures within the given ASC (S210).

The preamble retransmission counter is set at Preamble Retrans Max(S220), which is the maximum number of preamble retransmission attempts.The preamble transmission power is set at Preamble Initial Power (S230),which is the initial transmission power of the preamble. The preamble isthen transmitted according to the chosen uplink access slot, signatureand set transmission power (S240).

The UE 1 then determines whether the UTRAN 2 detected the preamble(S250). No random access message is transmitted if a NACK is detected inthe downlink access slot corresponding to the selected uplink accessslot. A random access message is transmitted if an ACK is detected inthe downlink access slot corresponding to the selected uplink accessslot. The preamble is retransmitted if no response, specifically neitheran ACK nor a NACK for the selected signature, is detected in thedownlink access slot corresponding to the selected uplink access slot.

TABLE VII Information Related to Physical Random-Access Procedure BeforeInitiation of Procedure Upon Initiating Procedure Preamble scramblingcode. Transport Format for PRACH message part. Message length in time(10 or 20 ms) ASC of the PRACH transmission AICH_Transmission_Timingparameter (0 or 1) Data to be transmitted (Transport Block Set) Set ofavailable signatures and set of available RACH sub-channels for eachAccess Service Class (ASC). Power-ramping factor Power Ramp Step(integer > 0) Preamble Retrans Max parameter (integer > 0) Initialpreamble power (Preamble_Initial_Power) Power offset in dB between powerof the last transmitted preamble and power of the control part of therandom-access message (P_(p-m) = P_(message-control) − P_(preamble)measured) Set of Transport Format parameters (including power offsetbetween the data part and the control part of the random-access messagefor each Transport Format)

When no response is received, the next available access slot is selectedfrom the random access subchannel within the given ASC (S260), a newsignature is randomly selected from the available signatures within thegiven ASC (S270), the preamble transmission power is increased by thestep width of the power ramping (Power Ramp Step) (S280) and thepreamble retransmission counter is reduced by 1 (S290). The UE 1 thendetermines if the maximum number of retransmissions have been attempted(S300). This preamble re-transmission procedure is repeated for as longas the preamble retransmission counter exceeds 0 and no response isreceived. The MAC is informed that no ACK was received on AICH (S310)and the physical layer random access procedure is terminated once theretransmission counter reaches 0.

If an ACK is received, the transmission power of the control channel ofthe random access message is set at a level higher than the transmissionpower of the last preamble transmitted according to a power offset(S320) and the random access message is transmitted 3 or 4 uplink accessslots after the uplink access slot of the last transmitted preambledepending on the AICH transmission timing parameter (S330). The higherlayer is then informed of the receipt of the ACK and transmission of therandom access message (S340) and the physical layer random accessprocedure is terminated.

If a NACK is received, no random access message is transmitted and nore-transmission of the preamble is performed. The MAC is informed that aNACK was received (S350) and the physical layer random access procedureis terminated.

FIG. 13 illustrates a signaling establishment procedure between a UE 1and UTRAN 2. As illustrated in FIG. 13, the RRC Connection Requestmessage is transmitted once the PRACH power control preambles have beenacknowledged (S400). The RRC Connection Request message includes areason for requesting the connection.

The UTRAN 2 determines which resources to reserve and performssynchronization and signaling establishment among radio network nodes,such as a NodeB 5 and serving RNC 4, depending on the request reason(S410). The UTRAN 2 then transmits the Connection Setup message to theUE 1, thereby conveying information about radio resource to use (S420).

The UE 1 confirms connection establishment by sending the ConnectionSetup Complete message to the UTRAN 2 (S430). The UE 1 transmits theInitial Direct Transfer message to the UTRAN 2 once the connection hasbeen established (S440). The Initial Direct Transfer message includesinformation such as the UE identity, UE current location and the kind oftransaction requested.

Authentication is then performed between the UE 1 and UTRAN 2 andsecurity mode communication is established (S450). The actual set upinformation is delivered to the UTRAN 2 from the UE 1 via the CallControl Setup message (S460). The Call Control Setup message identifiesthe transaction and indicates the QoS requirements.

The UTRAN 2 initiates activities for radio bearer allocation bydetermining if there are sufficient resources available to satisfy therequested QoS and transmits the Call Control Complete message to the UE1 (S470). The radio bearer is allocated according to the request ifthere are sufficient resources available. The UTRAN 2 may select eitherto continue allocation with a lowered QoS value, queue the request untilsufficient radio resources become available or reject the call requestif sufficient resources are not presently available.

The long-term evolution (LTE) of UMTS is under discussion by the 3rdgeneration partnership project (3GPP) that standardized UMTS. The 3GPPLTE is a technology for enabling high-speed packet communications. Manyschemes have been proposed for the LTE objective including those thataim to reduce user and provider costs, improve service quality, andexpand and improve coverage and system capacity.

The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement. Generally, The UTRAN 2 corresponds to E-UTRAN(Evolved-UTRAN). The NodeB 5 and/or RNC 4 correspond to e-NodeB in theLTE system. The following is the overview of the current LTE studyassumption for RACH.

The random access procedure is classified into two categories;non-synchronized random access and synchronized random access. Only thenon-synchronized random access procedure is considered herein.

Non-synchronized access is used when the uplink from a UE 1 has not beentime synchronized or when the UE uplink loses synchronization.Non-synchronized access allows the UTRAN 2 to estimate and adjust the UE1 transmission timing if necessary. Therefore the non-synchronizedrandom access preamble is used for at least time alignment and signaturedetection.

FIG. 14 illustrates a random access burst. The message payload mayinclude any additional associated signaling information, such as arandom ID, Pathloss/Channel Quality indicator (CQI), or access purpose.A message payload up to 6 bits is transmitted in the random access burstalong with the preamble as illustrated in FIG. 14.

A UE 1 randomly selects a signature from a group of signatures todistinguish between different UEs that attempt an access simultaneously.The preamble must have good auto-correlation properties in order for theUTRAN 2 to obtain an accurate timing estimate.

Additionally, different preambles should have good cross-correlationproperties in order for the UTRAN 2 to distinguish between simultaneousaccess attempts for different UEs 1 using different signatures. Aconstant amplitude zero auto-correlation (CAZAC) sequence is used as apreamble signature sequence to achieve good detection probability.

Layer 1 shall receive the information listed in Table VIII from thehigher layers prior to initiation of the non-synchronized physicalrandom access procedure. The information is transmitted as part of theSystem Information from higher layers.

TABLE VIII Information received from higher layers prior to initiationof the non-synchronized physical random access procedure Random accesschannel parameters (number, frequency position, time period, and timingoffset) Preamble format for the cell Number of root ZC sequences andsequence indices Preamble mapping to implicit message (set of causevalues, CQI quantization parameters, signature mapping) Power rampingstep size (note 0 dB step size is allowed) Maximum number of preambleretransmissions

FIG. 15 illustrates a call flow diagram for a non-synchronized physicalrandom access procedure. As illustrated in FIG. 15, the physical layer(L1) random access procedure encompasses successful transmission of therandom access preamble (message 1) and the random access response(message 2). The remaining messages are scheduled for transmission bythe higher layer on the shared data channel and thus are not consideredpart of the L1 random access procedure. A random access channel is a1.08 MHz portion of a subframe or set of consecutive subframes reservedfor random access preamble transmissions.

A random access channel is randomly selected from the availablenon-synchronized random access channels and a preamble sequence is thenrandomly selected from the available preamble set based on the messageto be transmitted. The random access procedure ensures that each of theallowed selections is chosen with equal probability.

The initial preamble transmission power level, which is set by the MAC,is determined using an open loop power control procedure. Thetransmission counter is set to the maximum number of preambleretransmissions.

A Random Access Preamble (message 1) is then transmitted using theselected random access channel, preamble sequence, and preambletransmission power. The L1 status “ACK on non-synchronized random accessreceived” is reported to the higher layers, such as the MAC, and thephysical random access procedure is terminated if a Random AccessResponse (message 2) corresponding to the transmitted preamble sequence(message 1) is detected. Another random access channel and preamble arerandomly selected if no Random Access Response (message 2) correspondingto the transmitted preamble sequence (message 1) is detected.

Preamble retransmission occurs as long as the maximum transmission powerand the maximum number of retransmissions have not been reached. The L1status “no acknowledgment on non-synchronized random access” is reportedto the higher layers, such as the MAC, and the physical random accessprocedure is terminated if the maximum transmission power or the maximumnumber of retransmissions has been reached.

The main purpose of the LTE (Long Term Evolution) random accessprocedure is to obtain uplink time synchronization and to obtain accessto the network.

A random access mechanism can be described where a preamble is sent froma UE1 to a NodeB 5 in order to determine the timing misalignment. Thepreamble structure is based on Zadoff-Chu sequences with ZeroCorrelation Zone (ZC-ZCZ) and different root sequence indices when therequired number of zones cannot be generated.

The zero-correlation zone for the ZC-ZCZ sequence is generated using acyclic shift version of the Zadoff-Chu (ZC) carrier sequence. Cyclicshifts within the same root sequence then form an ideal set ofsignatures for LTE RACH preambles since their cross-correlation is zero.

However, this is true only if the frequency error is small and for UEs 1with low mobility. The excellent properties of ZC-ZCZ sequencesdisappear as the frequency error increase for high-speed mobility UEs 1,thereby inducing overlapping between shifted sequences and making thesequence detection poor and impossible in some cases. Therefore, thecyclic shift is designed to avoid overlapping with the next shiftedposition when high-speed mobility UEs 1 are supported within the cell,which results in the use of a restricted set of cyclic shifts.

In other words the preamble cyclic shift length design differs for cellssupporting high-speed mobility UEs 1. In fact, the cyclic shift dependsnot only on cell size but is also proportional to sequence index whenthere is high Doppler.

Therefore, the LTE RACH preamble sequence design is different for lowand high mobility UEs 1. Furthermore, the conventional procedure doesnot use Zadoff-Chu sequences with Zero Correlation Zone (ZC-ZCZ)sequences for the RACH preamble.

For example, the WCDMA RACH preamble consists of 4096 chips, which is asequence of 256 repetitions of Hadamard codes of length 16 andscrambling codes. This facilitates simple and accurate frequency errorestimation then the same sequence design is used for both low and highspeed UEs 1.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a method of establishing acommunication link between a mobile terminal and a network is provided.The method includes receiving an indication of whether a communicationcell supports high speed mobility, generating sequences corresponding tosignatures available for random access and requesting access to thenetwork using a selected one of the generated sequences, wherein eitherthe sequences are generated according to whether high speed mobility issupported or the generated sequence is selected according to whetherhigh speed mobility is supported.

It is contemplated that the generated sequences are cyclic shiftedZadoff-Chu (ZC) sequences and further comprising mapping allowablesignatures onto the cyclic shifted ZC sequences. It is furthercontemplated that each available random access signature is mapped ontoa cyclic shifted ZC sequence using all possible cyclic shifted ZCsequences if high mobility is not supported. Preferably, each availablerandom access signature is mapped onto a cyclic shifted ZC sequenceusing a restricted set of all possible sequences, the restricted setdetermined according to a sequence index.

In another aspect of the present invention, a method of establishing acommunication link between a mobile terminal and a network is provided.The method includes generating sequences corresponding to signaturesavailable for random access, the sequences generated according to aprocess that either supports high mobility or does not support highspeed mobility, transmitting an indication of whether high speedmobility is supported, receiving an access request from a mobileterminal, the access request using a selected one of the generatedsequences and correlating the received request to each of the generatedsequences in order to determine which of the generated sequences wasused by the mobile terminal.

It is contemplated that the generated sequences are cyclic shiftedZadoff-Chu (ZC) sequences and further comprising mapping allowablesignatures onto the cyclic shifted ZC sequences. It is furthercontemplated that each available random access signature is mapped ontoa cyclic shifted ZC sequence using all possible cyclic shifted ZCsequences if high-speed mobility is not supported. Preferably, eachavailable random access signature is mapped onto a cyclic shifted ZCsequence using a restricted set of all possible sequences, therestricted set determined according to a sequence index.

In another aspect of the present invention, a method of establishing acommunication link between a mobile terminal and a network is provided.The method includes receiving an indication of whether a cell supportshigh-speed mobility and requesting access to the network using theindication, wherein the indication indicates information on restricteduse of cyclic shifts.

It is contemplated that the indication comprises one bit. It is furthercontemplated that requesting access to the network includes generatingsequences corresponding to signatures available for random access andrequesting access to the network using a selected one of the generatedsequences, wherein either the sequences are generated according whetherhigh speed mobility is supported or the generated sequence is selectedaccording to whether high speed mobility is supported. Preferably, thegenerated sequences are cyclic shifted Zadoff-Chu (ZC) sequences andfurther comprising mapping allowable signatures onto the cyclic shiftedZC sequences, each available random access signature mapped onto acyclic shifted ZC sequence using a restricted set of all possiblesequences, the restricted set determined according to the indication.

In another aspect of the present invention, a method of establishing acommunication link between a mobile terminal and a network is provided.The method includes transmitting an indication of whether a cellsupports high speed mobility and receiving a request to access thenetwork from the mobile terminal, wherein the indication indicatesinformation on restricted use of cyclic shifts and the request is basedon the indication.

It is contemplated that the indication comprises one bit. It is furthercontemplated that the method further includes generating sequencescorresponding to signatures available for random access, the sequencesgenerated according to a process that either supports high mobility ordoes not support high speed mobility, receiving the access request fromthe mobile terminal, the access request using a selected one of thegenerated sequences and correlating the received request to each of thegenerated sequences in order to determine which of the generatedsequences was used by the mobile terminal. Preferably, the generatedsequences are cyclic shifted Zadoff-Chu (ZC) sequences and furthercomprising mapping allowable signatures onto the cyclic shifted ZCsequences, each available random access signature mapped onto a cyclicshifted ZC sequence using a restricted set of all possible sequences,the restricted set determined according to the indication.

In another aspect of the present invention, a mobile terminal for ofestablishing a communication link with a network is provided. The mobileterminal includes a transmitting/receiving unit transmitting andreceiving messages between the mobile terminal and the network, adisplay unit displaying user interface information, an input unitreceiving inputs from a user and a processing unit processing a receivedindication of whether a communication cell supports high speed mobility,generating sequences corresponding to signatures available for randomaccess and controlling the transmitting/receiving unit to request accessto the network using a selected one of the generated sequences, whereinthe processing unit either generates the sequences according to whetherhigh speed mobility is supported or the selects the generated sequenceaccording to whether high speed mobility is supported.

It is contemplated that the generated sequences are cyclic shiftedZadoff-Chu (ZC) sequences and the processing unit further maps allowablesignatures onto the cyclic shifted ZC sequences. It is furthercontemplated that the processing unit maps each available random accesssignature onto a cyclic shifted ZC sequence using all possible cyclicshifted ZC sequences if high mobility is not supported. Preferably, theprocessing unit maps each available random access signature onto acyclic shifted ZC sequence using a restricted set of all possiblesequences, the restricted set determined according to a sequence index.

In another aspect of the present invention, a mobile terminal for ofestablishing a communication link with a network is provided. The mobileterminal includes a transmitting/receiving unit transmitting andreceiving messages between the mobile terminal and the network, adisplay unit displaying user interface information, an input unitreceiving inputs from a user and a processing unit processing a receivedindication of whether a cell supports high speed mobility andcontrolling the transmitting/receiving unit to request access to thenetwork using the indication, wherein the indication indicatesinformation on restricted use of cyclic shifts.

It is contemplated that the indication comprises one bit. It is furthercontemplated that processing unit controls the transmitting/receivingunit to request access to the network by generating sequencescorresponding to signatures available for random access and requestsaccess to the network using a selected one of the generated sequences,wherein the processing unit either generates the sequences according towhether high speed mobility is supported or the selects the generatedsequence according to whether high speed mobility is supported.Preferably, the generated sequences are cyclic shifted Zadoff-Chu (ZC)sequences and the processing unit maps allowable signatures onto thecyclic shifted ZC sequences, each available random access signaturemapped onto a cyclic shifted ZC sequence using a restricted set of allpossible sequences, the restricted set determined according to theindication.

In another aspect of the present invention, a network for establishing acommunication link with a mobile terminal is provided. The networkincludes a transmitter transmitting messages to the mobile terminal, areceiver receiving messages from the mobile terminal and a controllergenerating sequences corresponding to signatures available for randomaccess, controlling the transmitter to transmit an indication of whetherhigh speed mobility is supported, processing a received access requestfrom a mobile terminal that uses a selected one of the generatedsequences, and correlating the received request to each of the generatedsequences in order to determine which of the generated sequences wasused by the mobile terminal, wherein the controller generates thesequences according to a process that either supports high mobility ordoes not support high speed mobility.

It is contemplated that the generated sequences are cyclic shiftedZadoff-Chu (ZC) sequences and the controller maps allowable signaturesonto the cyclic shifted ZC sequences. It is further contemplated thatthe controller maps each available random access signature onto a cyclicshifted ZC sequence using all possible cyclic shifted ZC sequences ifhigh-speed mobility is not supported. Preferably, the controller mapseach available random access signature onto a cyclic shifted ZC sequenceusing a restricted set of all possible sequences, the restricted setdetermined according to a sequence index.

In another aspect of the present invention, a network for establishing acommunication link with a mobile terminal is provided. The networkincludes a transmitter transmitting messages to the mobile terminal, areceiver receiving messages from the mobile terminal and a controllercontrolling the transmitter to transmit an indication of whether a cellsupports high speed mobility and processing a received request to accessthe network from the mobile terminal, wherein the indication indicatesinformation on restricted use of cyclic shifts and the access request isbased on the indication.

It is contemplated that the indication comprises one bit. It is furthercontemplated that the controller further generates sequencescorresponding to signatures available for random access, the sequencesgenerated according to a process that either supports high mobility ordoes not support high speed mobility and correlates the received accessrequest to each of the generated sequences in order to determine whichof the generated sequences the mobile terminal used when sending theaccess request. Preferably, the generated sequences are cyclic shiftedZadoff-Chu (ZC) sequences and the controller maps allowable signaturesonto the cyclic shifted ZC sequences, each available random accesssignature mapped onto a cyclic shifted ZC sequence using a restrictedset of all possible sequences, the restricted set determined accordingto the indication.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. It is to beunderstood that both the foregoing general description and the followingdetailed description of the present invention are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

These and other embodiments will also become readily apparent to thoseskilled in the art from the following detailed description of theembodiments having reference to the attached figures, the invention notbeing limited to any particular embodiments disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 illustrates an overview of a UMTS network.

FIG. 2 illustrates a structure of a radio interface protocol between aUE and the UTRAN according to the 3GPP radio access network standards.

FIG. 3 illustrates the different logical channels.

FIG. 4 illustrates logical channels mapped onto transport channels asseen from the UE side.

FIG. 5 illustrates logical channels mapped onto transport channels asseen from the UTRAN side.

FIG. 6 illustrates a power ramping procedure.

FIG. 7 illustrates the number and spacing of access slots.

FIG. 8 illustrates the timing of the preamble, Access Indicator andmessage part.

FIG. 9 illustrates the structure of the random access message part.

FIG. 10 illustrates the structure of the AICH.

FIG. 11 illustrates a control access procedure.

FIG. 12 illustrates a physical layer random-access procedure.

FIG. 13 illustrates a signaling establishment procedure between a UE andnetwork.

FIG. 14 illustrates a random access burst.

FIG. 15 illustrates a call flow diagram for a non-synchronized physicalrandom access procedure.

FIG. 16 illustrates an example of possible channel response of indexes Mand (M+1) in a high Doppler environment.

FIG. 17 illustrates the relationship between a sequence index M andvarious circular shift approaches when high-speed mobility is supportedaccording to the present invention.

FIG. 18 illustrates channel response in high Doppler environments.

FIG. 19 illustrates a block diagram of a mobile station (MS) or accessterminal (AT) according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention allows a UE 1 to correctly map the signatureindexes onto the cyclic shifted ZC sequences when the deployed cellssupport a high-speed mobility UE 1. The present invention proposes toinform a UE 1 whether a cell supports high-speed mobility such that RACHsignatures may be correctly mapped onto the cyclic shifted ZC sequences.This information may either be broadcast on the system information in acell or fixed in the standard. Reference will now be made in detail tothe preferred embodiments of the present invention, examples of whichare illustrated in the accompanying drawings.

The ZC sequences of odd length N are defined by the following equation:au(k)=exp [−j2πM(k(k+1)/2N)], where:

-   -   N is a sequence length,    -   M=1 . . . N−1 is a root index of different sequences, and    -   k=0 . . . N−1 are indexes of the samples of a sequence.

ZC sequences have ideal correlation properties in the absence offrequency error, such that the periodic autocorrelation shows noside-peaks and the cross-correlation between two sequences withdifferent a root index M has a constant value when the index of thesamples of a sequence N is a prime number. Therefore, cyclic shifts of asequence form an ideal set of signatures for RACH preambles becausetheir cross-correlation is zero and they can all be detectedsimultaneously using frequency domain processing.

The number of cyclic shifts available for a single root index M dependson the length of the sequence and the propagation delay uncertainty: Theshift must be larger than the maximum propagation delay for given cellsizes.

However, this is true only if the frequency error is small, such as forlow-speed mobility UEs 1. The ZC sequences are quite sensitive to thefrequency error. The frequency error does not severely affect thecross-correlation between two ZC sequences but affects the detection ofcontiguous sequences due to overlapped channel response that cannot bediscriminated from each other, an example of which is illustrated inFIG. 16. The duration between the correct timing of the delay profile inFIG. 16, such as t for M and 2t for M+1, and the alias of the delayprofile, such as t-M and t+M, caused by large frequency offset in ahigh-speed mobility UE 1 is proportional to sequence index M.

Performance is improved if cyclic shifts in high Doppler environmentsare limited so that the cyclic shift pairs of each sequence perioduncertainty are not in the sequence period uncertainty of any RACHpreamble and the cyclic shift of t−1 of each sequence period uncertaintyis different from the cyclic shifts of t+1 of all sequences perioduncertainty. This results in using a restricted set of cyclic shifts forcells supporting high-speed mobility UEs 1.

The cyclic shift design may be done such that the alias channel responseis not overlapped with the other circular shift positions since thefrequency offset in a high-speed mobility UE 1 is proportional tosequence index M. Rules and methods of such design are known in the art.

The cyclic shift design is different depending upon whether a cellsupports high-speed mobility UEs 1. The basic random access procedure isfor a UE 1 to send a random access preamble (message 1), which carriesthe signature access to Node B 5. However, the access signature is onlysent to meet coverage requirement for non-synchronized random accesswithin the LTE framework.

The waveform of the LTE signature is based on Zadoff-Chu (ZC) withzero-correlation zones (ZCZ) and different mother sequence indexes whenthe required number of zones cannot be generated. This is because thenumber of ZCZ sequences is reduced inversely proportionally to cellradius. Therefore, additional ZCZ sequences from another index are addedwhen the number of ZCZ sequences insufficient.

The zero-correlation zones allow for ideal detection in the presence ofinterfering preambles. The optimal auto-correlation property of theCAZAC sequence is destroyed when the Doppler spread of a high-speedmobility UE 1 induces the frequency offset, thereby resulting indegraded detection performance. Doppler shift and frequency error on theuplink have properties depending on the channel condition, for example,line-of-site (LOS) condition or Non-line-of-site (NLOS) condition.

Frequency offset due to UE 1 mobility is spread over a range from thecarrier frequency In NLOS. Therefore, a UE 1 tracks around theAf_(BS)+Af_(uE) frequency offset. The frequency offset of the receiveduplink signal is nearly zero and one way Doppler spread can beconsidered.

The maximum frequency offset of the receiver signal In LOS, such as whena high-speed mobility vehicle moves towards or away from the EvolvedUMTS Terrestrial Radio Access Network (E-UTRAN) 2, is described as:f _(offset,UL) =Δf _(UE)+2f _(Doppler) _(—) _(max), where

f_(BS) denotes the base station frequency drift,

Δf_(UE) denotes UE 1 frequency error and

f_(Doppler) _(—) _(max) denotes the maximum Doppler frequency.

The worst-case frequency offset is around 1400 Hz with mobility of 350km/h at a 2 GHz carrier frequency. A UE 1 tracks around 650 Hz Dopplershift on the downlink in the LOS environment and then transmits uplinkdata compensated frequency offset in advance based on the estimatedfrequency offset on the downlink. Therefore, the frequency offset due toUE 1 mobility becomes twice of the Doppler shift of the channel at theNodeB 2, for example, 1300 Hz.

There may be two or three dominant components at the detection stage ifthere is frequency offset at the receiver due to Doppler spread orresidual frequency offset, as illustrated in FIG. 17. Therefore, thefrequency offset spreads the channel response over a wide rangedepending on the sequence index M that is used.

It is possible to predict where the channel response will occur iffrequency offset exists when the ZC sequence index is known. Thecircular shift should be designed such that the alias channel responseis not overlapped with the other circular shift positions. Therefore,the cyclic shift is depends not only on the cell size but also isproportional to the sequence index M, which results in the restrictedset of cyclic shifts as compared to the low Doppler case and also indifferent RACH signature mapping.

The methods and approaches regarding how to design the cyclic shiftswhen a cell supports high-speed mobility are known in the art. Forexample, rules for three different approaches are proposed.

The first approach is an “additional margin method” where:1≦M<2T ₀ and N−2T ₀ <M<N−1

The second approach is a “multiple circular shifts as one opportunitymethod” where:2T ₀ ≦M<└N/3┘ and N−└N/3┘<M≦N−2T ₀

The third approach is an “index selection method” where:└N/3┘≦M≦└2N/3┘

In all three approaches, N is a sequence length or ZC sequence length, Mis one sequence index or a ZC root index, and T₀ is the minimum cyclicshift for a given cell based on cell size. The necessary information,such as N, can be fixed in a standard while other information, such asT₀ and M, should be broadcast on the system information.

The present invention proposes that the network broadcast oneinformation bit to inform a UE 1 if high-speed mobility UEs issupported. This information bit would enable correct mapping of RACHsignatures onto the cyclic shifted ZC sequences. A UE 1 reads theinformation bit indicating support of high-speed mobility in a cell orindicating the use of a restricted set of cyclic shifts upon receiving abroadcast message relative to RACH information.

Information related to T₀ and M shall have already obtained by a UE 1from information broadcast by the E-UTRAN 2 before processing theinformation bit. The UE 1 shall have also already obtained informationrelated to N and the maximum number of RACH signatures from thebroadcast information if those values are not fixed by a standard. TheUE 1 then determines whether the information bit indicates thathigh-speed mobility is supported.

Mapping of RACH signatures onto the cyclic shifted ZC sequences can beeasily performed for each cell when high-speed mobility is notsupported, as indicated by the information bit having a value of “FALSE”or “0.” A UE 1 and E-UTRAN 2 can map RACH signatures onto the ZCsequences of index M, with RACH signatures incrementally mapped ontosubsequent cyclic-shifted versions by T_(o) of the same ZC sequenceuntil all possible cyclic shifts have been mapped for a given index M.New consecutive indexes M are added until the total number of signaturesequals a value specified in the standard or system information.

The E-UTRAN 2 may broadcast only one index M, with the UE 1 usingconsecutive indexes to generate the number of required preambles. Analternative is for the E-UTRAN 2 to broadcast a set of several indexes Mnot necessarily consecutive to each other, with the UE 1 using the firstindex within the set and then using consecutive indexes within the setand mapping signatures in the same manner by starting from a higher orlower sequence index.

Specifically, the UE 1 starts mapping RACH signatures onto the cyclicshifted ZC sequences by mapping onto the first ZC sequence of thereceived index M or on the first index M in a received list. The UE 1then incrementally maps the next subsequent signatures onto subsequentright-cyclic-shifted versions by the minimum cyclic shift length T₀ ofthe same ZC sequence index M until the maximum number of RACH signaturesis reached or all possible cyclic shifts of index M have been obtained.

The UE 1 maps the next signature onto the next ZC sequence index M+1 orthe next index in the list if the maximum number of RACH signatures isnot reached before all possible cyclic shifts of index M are used. TheUE 1 then maps the next subsequent signatures onto its subsequentright-cyclic-shifted versions by the minimum cyclic shift length T₀.This signature mapping is repeated over all ZC sequence indexes andstops when the maximum number of RACH signatures is reached.

The rules for using a restricted set of cyclic shifts for cellssupporting high-speed mobility UEs 1 are applied when the informationbit has a value of “TRUE” or “1.” These rules can be either fixed in astandard or broadcast by the E-UTRAN 2.

A UE 1 and the E-UTRAN 2 calculate the available cyclic shiftsproportional to the index M and add new consecutive indexes M+1 byadjusting the cyclic shifts proportionally until the total number ofsignatures equals a value specified in the standard or systeminformation. The relationship between the three cyclic shift approachesand the sequence index M is applied as illustrated In FIG. 18.

The E-UTRAN 2 may broadcast only one index M, with the UE 1 usingconsecutive indexes to generate the number of required preambles. Analternative is for the E-UTRAN 2 to broadcast a set of several indexes Mnot necessarily consecutive to each other, with the UE 1 using the firstindex within the set and then using consecutive indexes within the setand mapping signatures in the same manner by starting from a higher orlower sequence index and mapping signatures in the same manner byapplying the relationships illustrated in FIG. 18, starting from ahigher or lower sequence index.

Specifically, the UE1 starts mapping RACH signatures onto the cyclicshifted ZC sequences by determining, for received index M or for thefirst index M in a received list, the cyclic shift that can be appliedaccording to the restricted set of cyclic shifts that can be used. Thepreviously described rules are used as an example, but it should benoted that other possible rules for determining the restricted set ofcyclic shifts could be applied.

The UE 1 determines the minimum cyclic shift T_(min) according to thefirst approach if 1≦M<2T₀ or N−2T₀<M<N−1. The UE 1 determines theminimum cyclic shift T_(min) according to the second approach if2T₀≦M<└N/3┘ or N−└N/3┘<M≦N−2T₀. The UE 1 determines the minimum cyclicshift T_(min) according to the third approach if └N/3┘≦M≦└2N/3┘. Thedetermined T_(min) value is then set with the minimum cyclic shift ofindex M.

The UE 1 maps the first signature onto the first ZC sequence of thereceived index M or on the first index M in a received list. The UE 1then incrementally maps the next subsequent signatures onto subsequentright-cyclic-shifted versions by the minimum cyclic shift length T_(min)of the same ZC sequence index M until the maximum number of RACHsignatures is reached or all possible cyclic shifts of index M have beenobtained.

The UE 1 selects the next ZC sequence index M+1 or the next index in thelist and maps the next signature onto the ZC sequence of index M+1 orthe next index in the list if the maximum number of RACH signatures isnot reached before all possible cyclic shifts of index M are used. TheUE 1 determines the minimum cyclic shift T_(min) according to the firstapproach if 1≦(M+1)<2T₀ or N−2T₀<(M+1)<N−1. The UE 1 determines theminimum cyclic shift T_(min) according to the second approach if2T₀≦(M+1)<└N/3┘ or N−└N/3┘<(M+1)≦N−2T₀. The UE 1 determines the minimumcyclic shift T_(min) according to the third approach if└N/3┘≦(M+1)≦└2N/3┘. The determined T_(min) value is then set with theminimum cyclic shift of index M+1.

The determined T_(min) value is then set with the minimum cyclic shiftof index M+1. The UE 1 then incrementally maps the next subsequentsignatures onto subsequent right-cyclic-shifted versions by the minimumcyclic shift length T_(min) of the same ZC sequence index M+1 until themaximum number of RACH signatures is reached or all possible cyclicshifts of index M+1 have been obtained. This signature mapping isrepeated over all ZC sequence indexes and stops when the maximum numberof RACH signatures is reached.

FIG. 19 illustrates a block diagram of a mobile station (MS) or UE 1.The AT 2 includes a processor (or digital signal processor) 510, RFmodule 535, power management module 505, antenna 540, battery 555,display 515, keypad 520, memory 530, SIM card 525 (which may beoptional), speaker 545 and microphone 550.

A user enters instructional information, such as a telephone number, forexample, by pushing the buttons of a keypad 520 or by voice activationusing the microphone 550. The microprocessor 510 receives and processesthe instructional information to perform the appropriate function, suchas to dial the telephone number. Operational data may be retrieved fromthe Subscriber Identity Module (SIM) card 525 or the memory module 530to perform the function. Furthermore, the processor 510 may display theinstructional and operational information on the display 515 for theuser's reference and convenience.

The processor 510 issues instructional information to the RF module 535,to initiate communication, for example, transmits radio signalscomprising voice communication data. The RF module 535 comprises areceiver and a transmitter to receive and transmit radio signals. Anantenna 540 facilitates the transmission and reception of radio signals.Upon receiving radio signals, the RF module 535 may forward and convertthe signals to baseband frequency for processing by the processor 510.The processed signals would be transformed into audible or readableinformation outputted via the speaker 545, for example. The processor510 also includes the protocols and functions necessary to perform thevarious processes described herein.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims. Therefore, allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are intended to beembraced by the appended claims.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses.

The description of the present invention is intended to be illustrative,and not to limit the scope of the claims. Many alternatives,modifications, and variations will be apparent to those skilled in theart. In the claims, means-plus-function clauses are intended to coverthe structure described herein as performing the recited function andnot only structural equivalents but also equivalent structures.

What is claimed is:
 1. A method of establishing a communication linkbetween a user equipment (UE) and a network, the method comprising:receiving, by the UE, a high-speed related parameter from the network,the high-speed related parameter representing either TRUE or FALSE,wherein TRUE corresponds to a restricted set of cyclic shifts and FALSEcorresponds to an unrestricted set of cyclic shifts; if the high-speedrelated parameter represents TRUE, generating, by the UE, a first randomaccess preamble sequence using the restricted set of cyclic shifts; andtransmitting, by the UE, the generated first random access preamblesequence to the network, and if the high-speed related parameterrepresents FALSE, generating, by the UE, a second random access preamblesequence using the unrestricted set of cyclic shifts; and transmitting,by the UE, the generated second preamble sequence to the network,wherein the first random access preamble sequence and the second randompreamble sequence are generated from Zadoff-Chu (ZC) sequences with zerocorrelation zones.
 2. The method of claim 1, wherein the high-speedrelated parameter comprises one bit.
 3. A method of establishing acommunication link between a user equipment (UE) and a network, themethod comprising: transmitting, by the network, a high-speed relatedparameter to the UE, the high-speed related parameter representingeither TRUE or FALSE, wherein TRUE corresponds to a restricted set ofcyclic shifts and FALSE corresponds to an unrestricted set of cyclicshifts; and if the high-speed related parameter represents TRUE,receiving, by the network, a first random access preamble sequence fromthe UE, the first random access preamble sequence generated using therestricted set of cyclic shifts, and if the high-speed related parameterrepresents FALSE, receiving, by the network, a second random accesspreamble sequence from the UE, the second random access preamblesequence generated using the unrestricted set of cyclic shifts, whereinthe first random access preamble sequence and the second random preamblesequence are generated from Zadoff-Chu (ZC) sequences with zerocorrelation zones.
 4. The method of claim 3, wherein the high-speedrelated parameter comprises one bit.
 5. A user equipment forestablishing a communication link with a network, the UE comprising: aprocessing unit configured to: receive a high-speed related parameterfrom the network, the high-speed related parameter representing eitherTRUE or FALSE, wherein TRUE corresponds to a restricted set of cyclicshifts and FALSE corresponds to an unrestricted set of cyclic shifts; ifthe high-speed related parameter represents TRUE, generate a firstrandom access preamble sequence using the restricted set of cyclicshifts; and transmit the generated first random access preamble sequenceto the network, and if the high-speed related parameter representsFALSE, generate a second random access preamble sequence using theunrestricted set of cyclic shifts; and transmit the generated secondpreamble sequence to the network, wherein the first random accesspreamble sequence and the second random preamble sequence are generatedfrom Zadoff-Chu (ZC) sequences with zero correlation zones.
 6. The UE ofclaim 5, wherein the high-speed related parameter comprises one bit. 7.A network for establishing a communication link with a user equipment,the network comprising: a controller configured to: transmit ahigh-speed related parameter to the UE, the high-speed related parameterrepresenting either TRUE or FALSE, wherein TRUE corresponds to arestricted set of cyclic shifts and FALSE corresponds to an unrestrictedset of cyclic shifts; and if the high-speed related parameter representsTRUE, receive a first random access preamble sequence from the UE, thefirst random access preamble sequence generated using the restricted setof cyclic shifts, and if the high-speed related parameter representsFALSE, receive a second random access preamble sequence from the UE, thesecond random access preamble sequence generated using the unrestrictedset of cyclic shifts, wherein the first random access preamble sequenceand the second random preamble sequence are generated from Zadoff-Chu(ZC) sequences with zero correlation zones.
 8. The network of claim 7,wherein the high-speed related parameter comprises one bit.